[JUDGE3]

I have not seen an answer to this:

Pontiac left the Q-Jet behind and used a Holley on the great RA V engine.

so beings "engineers do stuff for reasons" what was the reasoning that GM went Holley here?

maybe this will settle the Q-Jet vs Holley debate once and for all?

[Sirrotica]

There's never going to be a clear cut answer to the question. I've run both on my race cars on a dirt track and prefer the Q jet for acceleration off of the corners, much crisper acceleration. On top end I see no real difference between the two makes of carburetors, at least on a dirt track, 400 and 428 cubic inch engines.

FWIW, I tried them with cast iron manifolds, and aluminum single plane and dual plane. I settled on a Torker I, with a divider plate, and a QJ.

I can't count the times I've had the hood off of the car and some passerby said that I'd gain performance with a holley, but after using both, I never saw and advantage to the holley, just my personal observations after using both.

[android 211]

Wasn't the RA V Holley an 850? Of course it would make more power at the top of the rpm curve.

[mgarblik]

Carburetor performance is all about calibration. Many manufacturers have gone the Holley route for short production, "special" engines. GM, Ford and Mopar, all have done this. Their is a certain "Street Cred", when Holley is spoken in the context of performance. Less so for Rochester, Carter, or Autolite/Motorctaft. Deserved or not, that's my observation over the last 50 years. Properly calibrated, A Q-jet vs a Holley would perform the same assuming the CFM requirements were met. The triple venturi in a Q-jet primary may give a slight fuel mileage advantage in low speed driving, not a concern in a Ram Air V engine.

[steve25]

The reason 98% of us back in the day loved our GM cars was the way they ran, and over the course of Pontiac production the Q-jet was used by far the most !
If they where good for 390 hp 428 motors then why are they viewed as not being good for a 550 hp motor when plenty of Super Stock cars have made over 600 hp with them?

I am just looking for a answer here based in fact and proven science, not emotional BS as in “ “ Holleys just look better” as is so many times put forth in these type of discussion’s!

[NeighborsComplaint]

Chevy always jumped over the fence to Holley when performance was the main criteria. Z28's. BBC and SBC over 325hp. Ford was always Holley with Autolite reserved for the low HP motors and a couple exceptions using a Quadrajet on the 429 where emissions came into play.

Buick and Olds were just like Pontiac, having retained their older engine architecture and intake designs (refined over the years) which favored the Quadrajet and provided the optimum performance for the application. Given a clean sheet of paper with RAV, they favored Holley. Mopar jumped from AFB to Holley and settled on Holley carburetors for their performance applications until emissions brought the Carter Thermoquad into play.

As others have said, I think the engineers found the Holleys easier to adapt and calibrate to the various performance requirements otherwise another brand would have been chosen.

[padgett]

Only problem with a QJ is the small float bowl needs a stronger fuel pump to avoid running dry near the end of a 1/4.

Personally never saw a Holly that didn't leak & prefer AFBs for dual quads.

[NeighborsComplaint]

I'll add that having lived through the muscle car era and having hung around guys with fast street cars and shops like Richter Automotive (Gold-Digger Funny Car), no one in those orbits ever replaced a Holley carburetor with a Quadrajet for increased performance.

[Tom Vaught]

My understanding is that the RA-V Carbs were 780 style #3310 "type" vacuum secondary carbs with some sources stating the cfm
was 800 cfm.
Since the typical 780 style carb could be rated as much as 20 cfm higher based on actual Flow Stand testing I will not argue with
that rating here.

I have no knowledge of a Pontiac RA-V carb ever being rated at 850 cfm.

Maybe 850 cfm when you ignore the Holley standard 20.4" of H2O test point and test at the "Hot Rod" 28" of H2O flow bench test pressure. We have discussed that marketing change many times.
At 20.4" of H2O test pressure the max cfm was about 780-800 cfm.

Tom V.

Those are FACTS. The typical Holley Modular Carb is a lot easier to "Modify" for increased performance, LOL, but the reality is CFM IS CFM
and for racing low speed drive-ability (which the Q-Jet excels at) is not part of the equation.
And companies were going to larger carbs each year, example the Dominator Ford Carbs in 1969. 1050 real cfm.

[Sirrotica]

By the same token, Royal Pontiac never ditched the Rochester carbs for a holley in their shootout tests. For a dual purpose application that consists of street, and racing, a Rochester is hard to beat. Ran them on race cars, and street cars and have tried holleys with nothing that appealed to me over a Rochester.

If I hadn't at least tried to run holley carbs on my street, and oval track cars my statements would be invalid, but I tried both.

For a engine that requires more CFM than a Rochester carb can deliver, you almost need to step up to something larger, so you have little options other than a dual quad setup with 2 small carbs, or a holley for the CFM required.

I've also always liked he Carter AFBs until the Pontiac displacement went over 400 cubes, the production AFBs were a choke point.

[Kenth]

The great RAV engine was never a production engine.
It was sold over the counter to racers, and racers were used to Holley carbs, so they got a Holley carb.
Not too many racers in the day understood the Quadrajet as they do today.

And, Pontiac used one of the most ultimate Quadrajets ever made on the 1973 455S.D.

[455dan]

One thing i can say, maybe a few others to.

I only almost burned my 1st Pontiac, a 67 4 speed GTO to the ground with a Holley... and later also my J-10 Honcho truck.

Not a Holley fan.
They seemed to want to design a very tunable carb But they designed "in" about every way they could for possible fuel leaks at multiple points.
Something I cant say for the Q jet equipped cars and trucks over the years.
With help from Cliff Ruggles Book give me a Qjet with some tricks and tuning on anything street driven, the gas mileage has also been better. YMMV

[tom s]

That pic is one of the 25 303 SCCA short deck Vs.Carbs were 780 vac secondary,most came with a 50CC acc pump,all had rear jet blocks.Tom

[72projectbird]

I prefer a Holley over any other carb. I find them easier to tune and like the large fuel bowls. That said, all carbs have their pros and cons.

If I'm building anything now, it's getting fuel injection.

[padgett]

" the production AFBs were a choke point" well one. However a pair of 750s (choke on rear, no choke on front) fits nicely on a dual quad manifold and progressive linkage is easy. Were a few cross ram Pontiacs. Inline Holleys would have to mount sideways.

[Tom Vaught]

Originally Posted by 455dan

One thing i can say, maybe a few others to.

I only almost burned my 1st Pontiac, a 67 4 speed GTO to the ground with a Holley... and later also my J-10 Honcho truck.

Not a Holley fan.
They seemed to want to design a very tunable carb But they designed "in" about every way they could for possible fuel leaks at multiple points.
Something I cant say for the Q jet equipped cars and trucks over the years.
With help from Cliff Ruggles Book give me a Qjet with some tricks and tuning on anything street driven, the gas mileage has also been better. YMMV

Carter Carbs and Rochester Carbs are "bathtub" style fuel bowl carbs.
Very hard unless a float/ needle/seat has an issue for them to have a
leaking fuel bowl.

Holley carbs are Modular Component carbs which use multiple gaskets.

On a single feed or dual feed carb you have two fuel bowl gaskets, two metering block or 2 fuel bowl gaskets and one metering block gasket and a metering plate gasket. IF YOU INSTALL THESE CORRECTLY AND APPLY THE CORRECT TORQUE TO THE GASKETS, THEY RARELY IF EVER LEAK.

If you are messing with a race car carb, and constantly changing things, eventually the gaskets will be compressed to the point where they need to be changed. Most street guys are lucky to change gaskets in their Holleys over a several year period. Or they use the old parts over and over again and create a potential leak point.

Mind you I probably have 1000 blue bowl gaskets in my carb work room as well as all of the other parts to properly build a carb. Never had a leak yet.
50+ years of running Holley carbs. Holley does have production torque specs for the bowls, base, etc.

Rochester 2-bbls seem to have the best rebuild success if you install the two check balls in the correct locations after the carb parts are cleaned correctly.

Tom V.

Holley/Q-jet debate sounds like a urination contest, everyone has an opinion and few actual facts.

[JUDGE3]

should have left off the word debate. was not my intention to debate pros/cons qjet vs holley.

I just wanted to know why Pontiac went holley on the RA V. fuel starvation with the q jet?

I notice in the RA V pic, it has a small bowl fuel pump also.

[Formulas]

Personally i hold the belief that both carbs are fine they just have their sweet spots, To me Qjet is a great street carb where low end throttle response and some resemblance of fuel mileage is paramount for stop and go driving and can be made to run well deep into some forms of racing

The tunnel port engines in my understanding were designed more for closed road course racing TRANS AM style where off idle response and gas mileage perhaps take a back seat to more constant WOT. and premium fuel distribution is paramount

just my take on it you would of had to been a fly on the wall in a certain room at a certain time to know exactly

.

[padgett]

Ford had a tunnel port in 67 soooo. 303 tunnel port was for SCCA Trans Am then a Canadian loophole let Pontiac use the Z-28 Chev. NASCAR had some interest in something similar but never panned out.

As for production, no way for the tunnel ports. Revs had to be over 4k before port velocity was enough for any torque and idle ? ***edaboudit.

Along with the SOHC 421s, just never made it.

QJ never had anything like what was needed particularly since design was for a square bore, MPG was never an issue. Doubt thaqt anyone considered a three barrel so conventional double pumper Holeys were the choice.

[JUDGE3]

being on the RA V topic then.

Have always read about the ports being to large, no velocity. that being the case, what is the best cubic inch/rpm engine for these heads?